<template>
  <div class="app">
    <mt-header fixed title="Vue -- demo">
      <router-link to="/" slot="left">
        <mt-button icon="back" @click="goback" v-show="isShow">返回</mt-button>
      </router-link>
    </mt-header>

   

    <nav class="mui-bar mui-bar-tab">
			<router-link class="mui-tab-item1 " to="/home">
				<span class="mui-icon mui-icon-home"></span>
				<span class="mui-tab-label">首页</span>
			</router-link>
			<router-link class="mui-tab-item1" to="/member">
				<span class="mui-icon mui-icon-contact"></span>
				<span class="mui-tab-label">会员</span>
			</router-link>
			<router-link class="mui-tab-item1" to="/cart">
				<span class="mui-icon mui-icon-extra mui-icon-extra-cart">
          <span class="mui-badge">{{goodsCount}}</span>
        </span>
				<span class="mui-tab-label">购物车</span>
			</router-link>
			<router-link class="mui-tab-item1" to="/search">
				<span class="mui-icon mui-icon-search"></span>
				<span class="mui-tab-label">搜索</span>
			</router-link>
		</nav>

   
    <!-- 存放子组件的容器 -->
    <router-view></router-view>

  </div>
</template>

<script>
export default {
  data() {
    return {
      isShow:false
      // goodsCount: 0 //计算属性的值不能在data中初始化
    }
  },
  methods: {
    goback() { // 点击后退(往后退一步)
      this.$router.go(-1);
    }
  },
    // 计算属性
  computed: {
    // 动态计算购物车徽标数量
    goodsCount() {
      // 购物车总数量初始值
      var count = 0;
      // 遍历每种商品，累加商品的总数量
      this.$store.state.car.forEach(item=>{
        count += item.count;
      })
      return count;
    }
  },
  // 一进来判断路由，解决刷新后退箭头的bug
  created() {
    // 监视路由的变化
    if(this.$route.path === "/home") {
      this.isShow = false;
    }else {
      this.isShow = true;
    }
  },
  // 监视
  watch: {
    // 监视路由的变化判断后退箭头的显示/隐藏
    "$route":function(newVal) {
      if(newVal.path === "/home") {
        this.isShow = false;
      }else {
        this.isShow = true;
      }
    }
  }
}
</script>

<style scoped>
.app {
  padding-top: 40px;
  padding-bottom: 50px;
}
/* 与图片分享组件的滑动导航栏类名冲突 */
.mui-bar-tab .mui-tab-item1.mui-active {
  color: #007aff;
}

.mui-bar-tab .mui-tab-item1 {
  display: table-cell;
  overflow: hidden;
  width: 1%;
  height: 50px;
  text-align: center;
  vertical-align: middle;
  white-space: nowrap;
  text-overflow: ellipsis;
  color: #929292;
}

.mui-bar-tab .mui-tab-item1 .mui-icon {
    top: 3px;
    width: 24px;
    height: 24px;
    padding-top: 0;
    padding-bottom: 0;
}

.mui-bar-tab .mui-tab-item1 .mui-icon~.mui-tab-label {
    font-size: 11px;
    display: block;
    overflow: hidden;
    text-overflow: ellipsis;
}
</style>